The invention pertains to a process for catalytically generating hydrogen-rich gases (frequently referred to as xe2x80x9csynthesis gasxe2x80x9d or xe2x80x9csyn gasxe2x80x9d) using a layered catalyst member in an autothermal reactor (also referred to in the prior art as an autothermal reformer).
Processes for catalytically partially oxidizing and/or catalytically steam reforming a hydrocarbon feed to produce hydrogen-rich gases are well known in the prior art. Typically, such processes utilize one reactor to catalytically partially oxidize a hydrocarbon feed to produce hydrogen-rich gases or to catalytically steam reform a hydrocarbon feed to produce hydrogen-rich gases. Alternatively, the prior art discloses processes for carrying out both the catalytic partial oxidation reaction and the catalytic steam reforming reaction in one autothermal reactor. Other prior art discloses carrying out both reactions in a single autothermal reactor containing catalyst zones within which each type of reaction is carried out. Exemplary prior art disclosing such processes include the following patents and published patent applications: U.S. Pat. Nos. 3,481,722; 3,976,507; 4,501,823; 4,522,894; 4,844,837; 4,927,857; 5,112,527; EP 0 112 613 A2; EP 0 495 534 A2; EP 0 673 074 B1; WO 96/00186; WO 99/48804; and WO 99/48805.
The prior art processes referred to above are more complex than the process of the present invention which may be carried out in a single autothermal reactor without the need to provide multiple sequential catalyst zones in the reactor. The catalytic partial oxidation reaction is exothermic in nature and the heat generated thereby is used to carry out the steam reforming reaction which is endothermic in nature. By having the catalytic partial oxidation layer(s) in intimate contact with the steam reforming catalyst layer(s), the process heat can be more effectively managed in an adiabatic reactor, i.e. an autothermal reactor. By having the two catalyst layers in contact with one another, heat loss which otherwise occurs from the use of multiple autothermal reactors or an autothermal reactor containing multiple catalyst zones is significantly minimized.
The process of the present invention also results in savings in reactor volume and monolith substrate costs as well as less pressure drop throughout the catalytic partial oxidation and steam reforming reactions. The process of the present invention thereby provides more efficient utilization and uniform usage of the heat generated by the exothermic catalytic partial oxidation reaction, thus allowing he endothermic steam reforming reaction to be carried out at a somewhat higher temperature due to lower heat loss and concomitant higher reaction rate and under adiabatic conditions. The result is that the catalytic partial oxidation reaction temperature is somewhat lowered, estimated to be by about 50 degrees and concomitantly, the steam reforming reaction temperature is estimated to be raised by about 50 degrees, thereby improving catalyst life and resulting in higher steam reforming reaction rates. Moreover, by utilizing the catalytic partial oxidation and steam reforming catalysts as layers in contact with one another, adverse reactions such as the reaction of oxygen with rhodium and the reaction of oxygen with platinum, may be avoided
An object of the present invention is to provide a process which will result in a more efficient generation of hydrogen-rich gases than prior art processes.
A further object of the present invention is to provide a process which will result in a more economical generation of hydrogen-rich gases than prior art processes.
The present invention pertains to the generation of hydrogen-rich gases by the following steps:
(a) introducing a preheated inlet stream comprising a hydrocarbon feed, water and air into an autothermal reactor containing a layered catalyst member and contacting the stream with the member at a temperature sufficient to initiate and sustain both catalytic partial oxidation and steam reforming (for the purposes of this invention, the term xe2x80x9cwaterxe2x80x9d will be understood to encompass xe2x80x9csteamxe2x80x9d);
(b) catalytically partially oxidizing at least part of the hydrocarbon feed to produce an effluent comprising hydrogen and carbon oxides; and
(c) steam reforming hydrocarbons remaining in the feed to produce a hydrogen-rich effluent.
The layered catalyst member comprises a monolith substrate containing on a surface thereof at least one layer of a steam reforming catalyst in contact with at least one layer of a catalytic partial oxidation catalyst. The steam reforming catalyst layer(s) and the catalytic partial oxidation catalyst layer(s) comprise the components described below.